Synthesis gas to hydrocarbon processes with neutral or negative carbon dioxide selectivity

ABSTRACT

A process for preparing C 2  to C 4  hydrocarbons includes introducing a feed stream into a reaction zone of a reactor, the feed stream comprising hydrogen gas and carbon monoxide. An additional stream is introduced into the reaction zone of the reactor, the additional stream comprising carbon dioxide. A combined stream that includes the feed stream and the additional stream is converted into a product stream comprising C 2  to C 4  hydrocarbons in the reaction zone in the presence of a hybrid catalyst. The hybrid catalyst includes a mixed metal oxide catalyst component, and a microporous catalyst component. The process operates at a gas hourly space velocity in excess of 2500 hr -1  and effectively yields a net carbon dioxide selectivity of less than 5.0% and a productivity of C 2 -C 4  hydrocarbons greater than 75 g hydrocarbons per kilogram of catalyst per hour.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Pat. ApplicationNo. 62/952,923, filed on Dec. 23, 2019, the entire disclosure of whichis hereby incorporated by reference.

BACKGROUND Field

The present specification generally relates to hybrid catalyst processesthat efficiently convert various carbon-containing streams to C₂ to C₄hydrocarbons. In particular, the present specification relates to hybridcatalyst processes that limit the amount of carbon dioxide (CO₂) that isproduced in the process. Generally, in hybrid catalyst processes, thesynthesis gas (syngas), or feed stream, comprises hydrogen (H₂) gas anda carbon-containing gas. A hybrid catalyst that is used in hybridcatalyst processes generally comprises a combination of a mixed metaloxide component and a molecular sieve that operate in tandem.

Technical Background

For a number of industrial applications, hydrocarbons are used, or arestarting materials used, to produce plastics, fuels, and variousdownstream chemicals. C₂ to C₄ hydrocarbons are particularly useful indownstream applications. A variety of processes for producing theselower hydrocarbons has been developed, including petroleum cracking andvarious synthetic processes.

Synthetic processes for converting feed carbon to desired products, suchas lower hydrocarbons, are known. Some of these processes includeco-feeding CO₂ to the process to reduce the net CO₂ selectivity,determined by the CO₂ in the product stream less the total CO₂ in thefeed stream, which may be negative. However, this approach typicallyleads to reduced productivity of the desired C₂ to C₄ hydrocarbons.

Accordingly, a need exists for processes and systems in which the netCO₂ selectivity is lower, while still having a sufficiently highproductivity of the desired C₂ to C₄ hydrocarbons.

SUMMARY

Embodiments of the present disclosure meet this need by utilizing syngasto prepare C₂ to C₄ hydrocarbons with a net CO₂ selectivity of less than5.0% by co-feeding CO₂ and operating at a gas hourly space velocity inexcess of 2500 hr⁻¹. According to one embodiment, a process forpreparing C₂ to C₄ hydrocarbons comprises: introducing a feed streaminto a reaction zone of a reactor, the feed stream comprising H₂ gas andcarbon monoxide (CO); introducing an additional stream into the reactionzone of the reactor, the additional stream comprising CO₂; andconverting a combined stream comprising the feed stream and theadditional stream into a product stream comprising C₂ to C₄ hydrocarbonsin the reaction zone in the presence of a hybrid catalyst, the hybridcatalyst comprising: a mixed metal oxide catalyst component; and amicroporous catalyst component, wherein the process operates at a gashourly space velocity greater than 2500 hr⁻¹, which results in a net CO₂selectivity of less than 5.0% and a productivity of C₂-C₄ hydrocarbonsgreater than 75 g hydrocarbons per kilogram of catalyst per hour.

Additional features and advantages will be set forth in the detaileddescription which follows, and in part will be readily apparent to thoseskilled in the art from that description or recognized by practicing theembodiments described herein, including the detailed description whichfollows and the claims.

It is to be understood that both the foregoing general description andthe following detailed description describe various embodiments and areintended to provide an overview or framework for understanding thenature and character of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view illustrating two streams being introduced toa reactor and one resulting product stream exiting the reactor inaccordance with one or more embodiments of the present disclosure.

FIGS. 2 and 3 graphically depict the thermodynamic relationship betweennet CO₂ selectivity and CO_(x) conversion when introducing a secondstream comprising CO₂ to the reactor.

DETAILED DESCRIPTION

As used herein, it is noted that “synthesis gas” and “syngas” areutilized herein to represent a mixture comprising primarily hydrogen,carbon monoxide, and very often some carbon dioxide.

Reference will now be made in detail to embodiments of processesutilizing syngas to prepare C₂ to C₄ hydrocarbons with a net CO₂selectivity of less than 5.0% and a productivity of C₂ to C₄hydrocarbons greater than 75 g hydrocarbons per kilogram of catalyst perhour by co-feeding CO₂ and operating at a gas hourly space velocity inexcess of 2500 hr⁻¹. As used herein, net CO₂ selectivity is defined asthe CO₂ exiting the reactor less the total CO₂ fed to the reactor. Inone embodiment, a process for preparing C₂ to C₄ hydrocarbons comprises:introducing a feed stream into a reaction zone of a reactor, the feedstream comprising H₂ gas and CO; introducing an additional stream intothe reaction zone of the reactor, the additional stream comprising CO₂;and converting a combined stream comprising the feed stream and theadditional stream into a product stream comprising C₂ to C₄ hydrocarbonsin the reaction zone in the presence of a hybrid catalyst, the hybridcatalyst comprising: a mixed metal oxide catalyst component; and amicroporous catalyst component, by operating at a gas hourly spacevelocity in excess of 2500 hr⁻¹ , resulting in a net selectivity of CO₂of less than 5.0% and a productivity of C₂ to C₄ hydrocarbons greaterthan 75 g hydrocarbons per kilogram of catalyst per hour. In someembodiments, the additional stream comprising CO₂ may be a recyclestream.

The use of an additional feed of CO₂ to reduce net CO₂ selectivity whenconverting feed streams comprising carbon to desired products, such as,for example, C₂ to C₄ hydrocarbons, is known. In general, in syngas tohydrocarbon processes, it is desirable to achieve a high productivity ofthe desired C₂ to C₄ hydrocarbons, while simultaneously reducing the netselectivity of CO₂. A known method to reduce the net selectivity of CO₂is by co-feeding CO₂. However, by co-feeding additional CO₂ to reducethe net selectivity of CO₂, this also results in a decreasedproductivity of the desired C₂ to C₄ hydrocarbons. However, the presentinventors have recognized that by operating the process at a high gashourly space velocity, for example, in excess of 2500 hr⁻¹, theadditional CO₂, while still reducing net selectivity of CO₂, does notinhibit production of the desired C₂ to C₄ hydrocarbons.

Processes according to embodiments disclosed and described hereinaddress the reduction of the net selectivity of CO₂ by introducing astream (referred to herein as the “additional stream”) in addition tothe feed stream, which may be, for example, syngas, wherein theadditional stream comprises CO₂, and operating the process at a high gashourly space velocity, which may be, for example in excess of 2500 hr⁻¹.As demonstrated herein, the addition of CO₂ to the process and operatingat a gas hourly space velocity in excess of 2500 hr⁻¹ lowers the netselectivity of CO₂, while maintaining a productivity of C₂ to C₄hydrocarbons greater than 75 g hydrocarbons per kilogram of catalyst perhour. Syngas to hydrocarbon process with neutral or negative CO₂selectivity according to embodiments will now be described in moredetail.

Referring to the embodiment of FIG. 1 , a feed stream 102 is fed into areaction zone 101, the feed stream 102 may comprise H₂ gas and CO. Inembodiments, the feed stream 102 is syngas. In some embodiments, the H₂gas is present in the feed stream 102 in an amount of from 20 volumepercent (vol%) to 80 vol%, based on combined volume of the H₂ gas andCO. In other embodiments, the H₂ gas is present in the feed stream 102in an amount from 40 vol% to 80 vol% or from 60 vol% to 80 vol%, basedon combined volume of H₂ gas and CO. The feed stream 102 is introducedinto a reaction zone 101 and contacted with a hybrid catalyst asdisclosed and described herein below in the reaction zone 101. Thehybrid catalyst comprises a mixed metal oxide catalyst component and amicroporous catalyst component.

Referring again to FIG. 1 , an additional stream 103 comprising CO₂ isintroduced into the reaction zone 101 with the feed stream 102. Inembodiments, the additional stream 103 may be added to the feed stream102 prior to introducing the feed stream 102 and additional stream 103into the reaction zone 101, such that a combined stream comprising thefeed stream 102 and the additional stream 103 are introduced into thereaction zone 101 simultaneously through the same inlet. In otherembodiments, the additional stream 103 may be added to the reaction zone101 through a different inlet than the feed stream 102, such that thefeed stream 102 and the additional stream 103 are not in contact untilboth are present in the reaction zone 101. In either of theabove-described embodiments, at some point during the syngas tohydrocarbon process both the feed stream 102 and the additional stream103 are present in the reaction zone 101 and are contacted with thehybrid catalyst.

As disclosed herein above, the combined stream may comprise H₂, CO, CO₂,or combinations thereof. The additional stream 103 is added to the feedstream 102, or introduced into the reaction zone 101 with the feedstream 102, so that the combined stream-comprising the feed stream 102and the additional stream 103—comprises from 10.0 vol% to 90.0 vol% H₂,such as from 10.0 vol% to 80.0 vol% H₂, from 10.0 vol% to 70.0 vol% H₂,from 10.0 vol% to 60.0 vol% H₂, from 10.0 vol% to 50.0 vol% H₂, from10.0 vol% to 40.0 vol% H₂, or from 10.0 vol% to 30.0 vol% H₂. In otherembodiments, the combined stream comprises from 20.0 vol% to 90.0 vol%H₂, such as from 30.0 vol% to y H₂, from 40.0 vol% to 90.0 vol% H₂, from50.0 vol% to 90.0 vol% H₂, or from 80.0 vol% to 90.0 vol% H₂. Yet inother embodiments, the combined stream comprises from 20.0 vol% to 80.0vol% H₂, such as from 40.0 vol% to 80.0 vol% H₂, or from 60.0 vol% to80.0 vol% H₂. In other embodiments, the combined stream comprises from45.0 vol% to 85.0 vol% H₂, such as from 55.0 vol% to 85.0 vol% H₂ orfrom 65.0 vol% to 85.0 vol% H₂. In providing a feed stream and anadditional stream to yield a combined feed stream having the above H₂content, the net CO₂ selectivity of the reaction can be controlled sothat the process using the additional stream 103 reduces the net CO₂selectivity.

In traditional syngas to hydrocarbons conversion processes, CO₂ is attimes co-fed to reduce net selectivity of CO₂. Without being bound toany particular theory, it is believed that the reduction in netselectivity of CO₂ is, at least in part, caused by manipulating theWater Gas Shift reaction (WGS) (CO + H₂O ←→ CO₂ + H₂). Balancing thereduced net CO₂ selectivity and the reduced CO_(x) conversion is, inembodiments, achieved by providing a combined stream comprising the feedstream 102 and the additional stream 103. However, by co-feeding CO₂,the productivity of the desired C₂-C₄ hydrocarbons is typically reducedcompared to when CO₂ is not co-fed. Thus, even though it is known toco-feed CO₂ to reduce the net selectivity of CO₂, the reduced netselectivity of CO₂ also results in lower productivity of C₂-C₄hydrocarbons. By operating the process at a high space velocity, whichis the subject of the present disclosure, co-feeding CO₂ results inreduced net selectivity of CO₂ while maintaining desired productivity ofthe desired C₂-C₄ hydrocarbons.

FIGS. 2 and 3 are based on thermodynamic equilibrium calculations andserve to further describe the additional feed of CO₂. FIG. 2 depicts therelationship between net CO₂ selectivity and CO_(x) conversion at 400°C. in a single-pass syngas to hydrocarbon process. In FIG. 2 , thevolume ratio of CO₂ and H₂ to CO in the feed stream was equal to three.However, when manipulating the WGS reaction, as depicted in FIG. 3 , therelationship between net CO₂ selectivity and CO_(x) conversion at 400°C. in a single-pass syngas to hydrocarbon process results in both lowernet CO₂ selectivity and higher CO_(x) conversions. For example, in FIG.3 , the 5% CO₂ - 50% approach to equilibrium (ATE) of the WGS reactionline produces a much lower net CO₂ selectivity when compared to the 5%CO₂ - 100% ATE of the WGS reaction line. In FIG. 3 , the volume ratio ofCO₂ and H₂ to CO in the feed stream was equal to five. When comparingFIGS. 2 and 3 , the different volume ratios of CO₂ and H₂ to CO in thefeed stream result in the 5% CO₂ lines differing between the two graphs.

As disclosed herein above, the additional stream 103, which may includea recycle stream 105, may comprise CO₂. It should be understood that theCO₂ introduced in the additional stream 103 is in addition to any CO₂present in the feed stream 102. The additional stream 103 is added tothe feed stream 102, or introduced into the reaction zone 101 with thefeed stream 102, so that the combined stream-comprising the feed stream102 and the additional stream 103—comprises from 3.0 vol% to 20.0 vol%CO₂, such as from 3.5 vol% to 20.0 vol% CO₂, from 4.0 vol% to 20.0 vol%CO₂, from 4.5 vol% to 20.0 vol% CO₂, from 5.0 vol% to 20.0 vol% CO₂,from 5.5 vol% to 20.0 vol% CO₂, from 6.0 vol% to 20.0 vol% CO₂, from 6.5vol% to 20.0 vol% CO₂, from 7.0 vol% to 20.0 vol% CO₂, from 7.5 vol% to20.0 vol% CO₂, from 8.0 vol% to 20.0 vol% CO₂, from 8.5 vol% to 20.0vol% CO₂, from 9.0 vol% to 20.0 vol% CO₂, from 9.5 vol% to 20.0 vol%CO₂, from 10.0 vol% to 20.0 vol% CO₂, from 10.5 vol% to 20.0 vol% CO₂,from 11.0 vol% to 20.0 vol% CO₂, from 11.5 vol% to 20.0 vol% CO₂, from12.0 vol% to 20.0 vol% CO₂, from 12.5 vol% to 20.0 vol% CO₂, from 13.0vol% to 20.0 vol% CO₂, from 13.5 vol% to 20.0 vol% CO₂, from 14.0 vol%to 20.0 vol% CO₂, from 14.5 vol% to 20.0 vol% CO₂, from 15.0 vol% to20.0 vol% CO₂, from 15.5 vol% to 20.0 vol% CO₂, from 16.0 vol% to 20.0vol% CO₂, from 16.5 vol% to 20.0 vol% CO₂, from 17.0 vol% to 20.0 vol%CO₂, from 17.5 vol% to 20.0 vol% CO₂, from 18.0 vol% to 20.0 vol% CO₂,from 18.5 vol% to 20.0 vol% CO₂, from 19.0 vol% to 20.0 vol% CO₂, orfrom 19.5 vol% to 20.0 vol% CO₂. In some embodiments, the combinedstream comprises from 3.0 vol% to 19.5 vol% CO₂, such as from 3.0 vol%to 19.0 vol% CO₂, from 3.0 vol% to 18.5 vol% CO₂, from 3.0 vol% to 18.0vol% CO₂, from 3.0 vol% to 17.5 vol% CO₂, from 3.0 vol% to 17.0 vol%CO₂, from 3.0 vol% to 16.5 vol% CO₂, from 3.0 vol% to 16.0 vol% CO₂,from 3.0 vol% to 15.5 vol% CO₂, from 3.0 vol% to 15.0 vol% CO₂, from 3.0vol% to 14.5 vol% CO₂, from 3.0 vol% to 14.0 vol% CO₂, from 3.0 vol% to13.5 vol% CO₂, from 3.0 vol% to 13.0 vol% CO₂, from 3.0 vol% to 12.5vol% CO₂, from 3.0 vol% to 12.0 vol% CO₂, from 3.0 vol% to 11.5 vol%CO₂, from 3.0 vol% to 11.0 vol% CO₂, from 3.0 vol% to 10.5 vol% CO₂,from 3.0 vol% to 10.0 vol% CO₂, from 3.0 vol% to 9.5 vol% CO₂, from 3.0vol% to 9.0 vol% CO₂, from 3.0 vol% to 8.5 vol% CO₂, from 3.0 vol% to8.0 vol% CO₂, from 3.0 vol% to 7.5 vol% CO₂, from 3.0 vol% to 7.0 vol%CO₂, from 3.0 vol% to 6.5 vol% CO₂, from 3.0 vol% to 6.0 vol% CO₂, from3.0 vol% to 5.5 vol% CO₂, from 3.0 vol% to 5.0 vol% CO₂, from 3.0 vol%to 4.5 vol% CO₂, from 3.0 vol% to 4.0 vol% CO₂, or from 3.0 vol% to 3.5vol% CO₂. In still other embodiments, the combined stream comprises from3.5 vol% to 19.5 vol% CO₂, such as from 4.0 vol% to 19.0 vol% CO₂, from4.5 vol% to 18.5 vol% CO₂, from 5.0 vol% to 18.0 vol% CO₂, from 5.5 vol%to 17.5 vol% CO₂, from 6.0 vol% to 17.0 vol% CO₂, from 6.5 vol% to 16.5vol% CO₂, from 7.0 vol% to 16.0 vol% CO₂, from 7.5 vol% to 15.5 vol%CO₂, from 8.0 vol% to 15.0 vol% CO₂, from 8.5 vol% to 14.5 vol% CO₂,from 9.0 vol% to 14.0 vol% CO₂, from 9.5 vol% to 13.5 vol% CO₂, from10.0 vol% to 13.0 vol% CO₂, from 10.5 vol% to 12.5 vol% CO₂, or from11.0 vol% to 12.0 vol% CO₂. By providing a feed stream and an additionalstream 103 comprising CO₂ to yield a combined feed stream having theabove CO₂ content, the net CO₂ selectivity of the process can becontrolled.

In embodiments where the additional stream 103 comprises CO₂, it shouldbe understood that the CO₂ introduced in the additional stream 103 is inaddition to any CO₂ present in the feed stream 102. The additionalstream 103 may comprise any amount CO₂ such that the combinedstream-comprising the feed stream 102 and the additional stream 103—hasthe concentrations of CO₂ as disclosed hereinabove.

Introducing an additional stream 103 comprising CO₂ with the feed stream102, such as, for example, syngas (H₂+CO), reduces the net CO₂selectivity. Although only co-feeding CO₂ reduces the net CO₂selectivity, only introducing CO₂ in the additional stream 103 alsodecreases the level of conversion of carbon to desired products (such asthe conversion of feed carbon to any carbon-containing product that isnot CO or CO₂, also referred to herein as CO_(x) conversion). However,it was found that introducing an additional stream 103 comprising CO₂together with the feed stream 102, such as, syngas and operating at ahigh gas hourly space velocity effectively reduces the net CO₂selectivity, and significantly lowers the impact on hydrocarbonproductivity, compared to the cases operated at a lower space velocity.

In embodiments, the combined stream comprising the additional stream 103and the feed stream 102 may have an CO₂/CO volume ratio from 0.05 to1.50, such as from 0.05 to 1.50, from 0.15 to 1.50, from 0.25 to 1.50,from 0.35 to 1.50, from 0.45 to 1.50, from 0.65 to 1.50, from 0.75 to1.50, from 0.85 to 1.50, from 0.95 to 1.50, from 1.05 to 1.50, from 1.15to 1.50, from 1.25 to 1.50, from 1.35 to 1.50, or from 1.45 to 1.50. Inother embodiments, the combined stream comprising the additional stream103 and the feed stream 102 may have a CO₂/CO volume ratio from 0.05 to1.40, such as from 0.05 to 1.30, from 0.05 to 1.20, from 0.05 to 1.10,from 0.05 to 1.00, from 0.05 to 0.90, from 0.05 to 0.80, from 0.05 to0.70, from 0.05 to 0.60, from 0.05 to 0.50, from 0.05 to 0.40, from 0.05to 0.30, from 0.05 to 0.20, or from 0.05 to 0.10. In yet otherembodiments, the combined stream comprising the additional stream 103and the feed stream 102 may have a CO₂/CO volume ratio from 0.10 to1.40, such as from 0.20 to 1.30, from 0.30 to 1.20, from 0.40 to 1.10,from 0.50 to 1.00, from 0.60 to 0.90, or from 0.70 to 0.80. In stillother embodiments, the combined stream comprising the additional stream103 and the feed stream 102 may have a CO₂/CO from 0.20 to 1.35, such asfrom 0.35 to 1.20, from 0.50 to 1.05, from 0.65 to 0.90, or from 0.70 to0.80. The ratio of CO₂/CO must be high enough that there is sufficientCO₂ to convert carbon to C₂ to C₄ hydrocarbons and significantlydecrease the net CO₂ selectivity.

The reaction conditions within the reaction zone 101 will now bedescribed. The feed stream 102 and the additional stream 103 arecontacted with the hybrid catalyst in the reaction zone 101 underreaction conditions sufficient to form a product stream 104 comprisingC₂ to C₄ hydrocarbons. In some embodiments, the C₂ to C₄ hydrocarbonsconsist essentially of C₂ to C₄ olefins. The reaction conditionscomprise a temperature within reaction zone 101 ranging, according toone or more embodiments, from 300° C. to 500° C., such as from 380° C.to 450° C., from 380° C. to 440° C., from 380° C. to 430° C., from 380°C. to 420° C., from 380° C. to 410° C., from 380° C. to 400° C., or from380° C. to 390° C. In other embodiments, the temperature within thereaction zone 101 is from 390° C. to 450° C., from 400° C. to 450° C.,from 410° C. to 450° C., from 420° C. to 450° C., from 430° C. to 450°C., or from 440° C. to 450° C. In yet other embodiments, the temperaturewithin the reaction zone 101 is from 380° C. to 450° C., such as from390° C. to 440° C., from 400° C. to 430° C., or from 410° C. to 420° C.

The reaction conditions also, in embodiments, include a pressure insidethe reaction zone 101 of at least 20 bar (20,000 kilopascals (kPa)),such as at least 25 bar (25,000 kPa), at least 30 bar (30,000 kPa), atleast 35 bar (35,00 kPa), at least 40 bar (40,000 kPa), at least 45 bar(45,000 kPa), at least 50 bar (50,000 kPa), at least 55 bar (55,000kPa), at least 60 bar (60,000 kPa), at least 65 bar (65,000 kPa), or atleast 70 bar (70,000 kPa). In other embodiments, the reaction conditionsinclude a pressure inside the reaction zone 101 from 20 bar (20,000 kPa)to 70 bar (70,000 kPa), such as from 25 bar (25,000 kPa) to 65 bar(65,000 kPa), or from 30 bar (30,000 kPa) to 60 bar (60,000 kPa), from35 bar (35,000 kPa) to 55 bar (55,000 kPa), from 40 bar (40,000 kPa) to50 bar (50,000 kPa).

The reaction conditions also, in embodiments, include a gas hourly spacevelocity inside the reaction zone 101 of at least 2500 hr⁻¹, such as atleast 3000 hr⁻¹, such as at least 3600 hr⁻¹, such as at least 4200 hr⁻¹,such as at least 4800 hr⁻¹, such as at least 5400 hr⁻¹, such as at least6000 hr⁻¹, such as at least 6600 hr⁻¹, or such as at least 7200 hr⁻¹.

In embodiments, the reaction may have a net CO₂ selectivity of less than5.0%, less than 4.0%, less than 3.0%, less than 2.0%, or less than 1.0%,or even a negative net CO₂ selectivity, such as less than 0.0%.

The hybrid catalyst used in the above-disclosed processes will now bedescribed. Referring to FIG. 1 , hybrid catalyst systems comprise amixed metal oxide catalyst component, which converts the feed stream 102and additional stream 103 to oxygenated hydrocarbons, and a microporouscatalyst component (such as, for example, a zeolite component), whichconverts the oxygenates to hydrocarbons. The hybrid catalyst, accordingto embodiments, comprises a mixed metal oxide catalyst component inadmixture with a microporous catalyst component that may be selectedfrom molecular sieves having 8-MR pore access and having a frameworktype selected from the group consisting of the following framework typesCHA, AEI, AFX, ERI, LTA, UFI, RTH, RHO, LEV, and combinations thereof,the framework types corresponding to the naming convention of theInternational Zeolite Association. It should be understood that inembodiments, both aluminosilicate and silicoaluminophosphate frameworksmay be used. In certain embodiments, the molecular sieve may be SAPO-34silicoaluminophosphate having a Chabazite (CHA) framework type.

Examples of these may include, but are not necessarily limited to: CHAembodiments selected from SAPO-34 and SSZ-13; and AEI embodiments suchas SAPO-18. Combinations of microporous catalyst components having anyof the above framework types may also be employed. It should beunderstood that the microporous catalyst component may have a differentmembered ring pore opening depending on the desired product. Forinstance, microporous catalyst component having 8-MR to 12-MR poreopenings could be used depending on the desired product. However, toproduce C₂ to C₄ hydrocarbons, a microporous catalyst component having8-MR pore openings is used in embodiments.

In one or more embodiments, the mixed metal oxide catalyst component maybe a bulk catalyst or a supported catalyst and may be made by anysuitable method, such as co-precipitation, impregnation, or the like. Inembodiments, the mixed metal oxide catalyst component comprises gallium(Ga). In embodiments, the mixed metal oxide catalyst component compriseszirconium (Zr). It should be understood that any metal in the mixedmetal oxide component mixture can be present in a variety of oxidationstates. It should also be understood that the designation of a specificoxide (e.g. Ga₂O₃), does not necessarily preclude the presence of anadditional or different oxide of the given metal(s).

The mixed metal oxide catalyst component and the microporous catalystcomponent of the hybrid catalyst may be mixed together by any suitablemeans, such as, for example, by physical mixing-such as shaking,stirring, or other agitation. In other embodiments, the mixed metaloxide catalyst component and the microporous catalyst component may bepresent as a single formulated catalyst. The mixed metal oxide catalystcomponent and the microporous catalyst component may be present in thereaction zone 101, typically as a hybrid catalyst in a catalyst bed, ina weight/weight (wt/wt) ratio (mixed metal oxide catalyst component :microporous catalyst component) ranging from 0.1:1 to 10:1, such as from0.5:1 to 9:1.

In embodiments, the mixed metal oxide catalyst component may be reducedwithin the reactor prior to exposure to the feed stream 102 by exposingthe mixed metal oxide catalyst component to conventional reducing gases.In other embodiments, the mixed metal oxide catalyst component may bereduced within the reactor upon exposure to reducing gases in the feedstream 102 such as H₂ and CO.

EXAMPLES

Embodiments will be further clarified by the following examples.

Example 1 and Comparative Examples 1 to 3

Various performance tests were carried out at 30 bar (3.0 MPa), at atemperature of 420° C., and at a gas hourly space velocities of at least2500 hr⁻¹. These performance tests were completed by flowing a streamcomprising syngas and a stream comprising CO₂ to yield a combined streamwith the desired CO₂:CO ratio as shown in Table 1 over a catalystcomprising a mixed metal oxide catalyst component and a microporouscatalyst component. In these performance tests, the mixed metal oxidecatalyst component comprised gallium and the microporous catalystcomponent comprised SAPO-34. The results are shown in Table 1 below. Thereactor effluent composition was obtained by gas chromatography and theCO_(x) conversion was calculated using the following equation:

$\begin{array}{l}{\text{CO}_{\text{x}}\text{Conversion} = \text{X}_{\text{CO}_{\text{X}}}\left( \text{\%} \right) = \left\lbrack \left( {\text{n}_{\text{CO, in}} + \text{n}_{\text{CO2, in}} - \text{n}_{\text{CO, out}} -} \right. \right.} \\{\left. {\left. \text{n}_{\text{CO2, out}} \right)\text{/}\left( {\text{n}_{\text{CO, in}} + \text{n}_{\text{CO2, in}}} \right)} \right\rbrack \cdot 100.}\end{array}$

In equation (1), n_(CO) and n_(CO2) are the molar flows of CO and CO₂respectively.

For net CO₂ consumption (CO₂ selectivity < 0), the net selectivity ofproduct j where e.g.

$\begin{array}{l}{\left. {\text{j} = \text{hydrocarbons and oxygenates}} \right)\text{: S}_{\text{j}}\left( \text{\%} \right) = \left\lbrack \left\lbrack {\left( \text{aj * n}_{\text{j, out}} \right)\text{/}} \right. \right.} \\{\left. \left( {\text{n}_{\text{CO, in}} - \text{n}_{\text{CO, out}} + \text{n}_{\text{CO2, in}} - \text{n}_{\text{CO2, out}}} \right) \right\rbrack \cdot 100.}\end{array}$

$\begin{array}{l}{\text{For net CO}_{\text{2}}\text{Production}\left( {\text{CO}_{\text{2}}\text{selectivity > 0}} \right)\text{, the net selectivity}} \\{\text{of CO}_{\text{2}}\text{: S}_{\text{CO2}}\left( \text{\%} \right) = \left\lbrack \left\lbrack {\left( {\text{n}_{\text{CO2, out}} - \text{n}_{\text{CO2, in}}} \right)\text{/}\left( {\text{n}_{\text{CO, in}} -} \right.} \right. \right.} \\{\left. \left. \text{n}_{\text{CO, out}} \right) \right\rbrack \cdot 100.}\end{array}$

$\begin{array}{l}{\text{For net CO}_{\text{2}}\text{production}\left( {\text{CO}_{\text{2}}\text{selectivity > 0}} \right)\text{, the net selectivity}} \\{\left. {\text{of product j where, e}\text{.g}\text{. j} = \text{hydrocarbons and oxygenates}} \right)\text{:}} \\{\text{S}_{\text{j}}\left( \text{\%} \right) = \left\lbrack \left\lbrack {\left( {\text{a}_{\text{j}}\text{* n}_{\text{j, out}}} \right)\text{/}\left( {\text{n}_{\text{CO, in}} - \text{n}_{\text{CO, out}}} \right)} \right\rbrack \right. \cdot 100.}\end{array}$

For net CO₂-neutral operation, both equations are equal with S_(CO2) (%)= 0.

In equations (2)and (4), a is the number of carbon atoms for product jand n_(j),_(out) is the molar outlet of product j.

Table 1 Example Combined Stream Composition (% H₂/% CO₂/% CO) MixedMetal Oxide Catalyst Component (mg) Microporous Catalyst Component (mg)GHSV (hr⁻¹) CO_(x) Conversion (%) Net CO₂ Selectivity (%) C₂-C₄ OlefinProductivity (g/kg cat/hr) Ex. 1 69.9/8.6/21.5 120.1 39.9 5000 19.6 3.5121.0 Comp Ex. 1 69.9/8.6/21.5 200.1 100.1 3200 24.8 14 102.3 Comp. Ex.2 81.25/0/18.7 5 133.4 133.3 3300 42 27.3 83.2 Comp. Ex. 3 69.9/8.6/21.5240.1 80.1 2500 25.1 16.8 79.6

As can be seen in Table 1, Comparative Examples 1-3 do not yield a netCO₂ selectivity less than 5.0%. However, Example 1 demonstrates a netCO₂ selectivity of less than 5.0 % when operating in the presence ofless catalyst, which leads to a higher gas hourly space velocity thanComparative Example 1. Although the absolute numbers for the net CO₂selectivity will differ with process conditions, the examples show ageneral trend that the net CO₂ selectivity decreases as the CO₂ co-fedto the reactor is increased and the process is operated at a high gashourly space velocity. As can be seen from Comparative Examples 1 and 2,with a decrease in the amount of CO₂ fed to the reactor, even operatingat a higher space velocity does not result in a net CO₂ selectivity lessthan 5.0%.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the embodiments describedherein without departing from the spirit and scope of the claimedsubject matter. Thus, it is intended that the specification cover themodifications and variations of the various embodiments described hereinprovided such modification and variations come within the scope of theappended claims and their equivalents.

1. A process for preparing C₂ to C₄ hydrocarbons comprising: introducinga feed stream comprising hydrogen gas and a carbon-containing gascomprising carbon monoxide into a reaction zone of a reactor;introducing a second stream comprising carbon dioxide into the reactionzone of the reaction; forming a combined stream from the feed and secondstream; converting the combined stream into a product stream comprisingC₂ to C₄ hydrocarbons in the reaction zone in the presence of a hybridcatalyst, the hybrid catalyst comprising: a mixed metal oxide catalystcomponent; and a microporous catalyst component, wherein a gas hourlyspace velocity (GHSV) is at least 2500 hr⁻¹, a net CO₂ selectivity isless than 5.0%, and a C₂ to C₄ hydrocarbon productivity of at least 75 ghydrocarbon/kg catalyst per hour.
 2. The process of claim 1, wherein thesecond stream comprises up to 80.0 v% CO₂.
 3. The process of claim 1,wherein the second stream consists of CO₂.
 4. The process of claim 1,wherein the combined stream comprises greater than 6.3 v% CO₂.
 5. Theprocess of claim 1, wherein the combined stream comprises 50 v% to 80 v%hydrogen.
 6. The process of claim 1, wherein the combined streamcomprises a carbon dioxide (CO₂)/carbon monoxide (CO) volume ratio(CO₂/CO) from 0.05 to 1.5 v/v.
 7. The process of claim 1, wherein thereaction zone operates at a temperature from 380° C. to 450° C.
 8. Theprocess of claim 1, wherein the reaction zone operates at a pressurefrom 20 bar to 70 bar.
 9. The process of claim 1, wherein the GHSV isgreater than 4800 hr⁻¹.
 10. The process of claim 1, wherein the mixedmetal oxide catalyst component comprises ZrO₂.
 11. The process of claim1, wherein the mixed metal oxide catalyst component comprises ZrO₂ andGa₂O₃.
 12. The process of claim 1, wherein the microporous catalystcomponent is a molecular sieve having 8-MR pore openings.
 13. Theprocess of claim 1, wherein the microporous catalyst component isSAPO-34.
 14. The process of claim 1, wherein the net CO₂ selectivity isless than 1.0%.
 15. The process of claim 1, wherein the C₂ to C₄hydrocarbons consist essentially of C₂ to C₄ olefins.